VMware struck first. Today the company rolled out Fusion 5, which formally supports OS X Mountain Lion as both a host and guest and adds Windows Server 2012 and Ubuntu 12.04 to the guest list. (The previous version works with Mountain Lion as well, but without official support or full compatibility.)

A new Professional edition lets admins create restricted virtual machine images that lock down VM settings and data, and (using VMware Player) can be run on Windows, Linux, or OS X hosts. Fusion 5 Professional also borrows a developer-friendly feature from VMware Workstation: a virtual network editor that allows you to configure custom networks among virtual machines, either isolated or connected to the outside world. Fusion now also provides performance counters for virtual machines, giving developers valuable information for squeezing maximum efficiency out of software applications.

Designed for Mountain Lion, Fusion 5 meshes with a number of Mountain Lion features. You can search Windows apps, as well as OS X apps in the Launchpad. Fusion also sends its alerts to Mountain Lion's Notification Center. On top of the Mountain Lion compatibility, VMware has injected Fusion 5 with enhanced support for the MacBook Pro with Retina display, along with support for USB 3.0 connectivity.

As for Windows 8, Fusion 5 supports the Standard, Pro, and Enterprise versions of the new operating system. (In the previous version, you could install Windows 8 as if it were a Windows 7 environment.) In addition to running Windows 8 VMs, Fusion 5 can also run Windows 8 from a Boot Camp partition. Unity mode -- which displays Windows and OS X apps side by side in separate Finder windows -- takes on a new twist with Windows 8: The Metro Start screen fills the entire Mac display, just as it does in Windows.

VMware Fusion 5 Professional includes all the features from the standard edition, along with capabilities aimed at helping IT professionals get a better handle on heterogeneous and BYOD desktop environments. By configuring restricted virtual machines, admins can prevent users from changing VM settings, copying data between the VM and host environments, or attaching USB devices to the Windows VM.

Separately, VMware also took the wraps off VMware Workstation 9, adding support for Windows 8, restricted VM features, and a new Web interface that allows remote, browser-based access to the virtual machine catalog and running VMs. Like Fusion 5, Workstation 9 brings USB 3.0 support to Windows 8 VMs, compatibility with Intel's new Ivy Bridge CPUs, virtual performance counters, and support for 3D graphics based on OpenGL 2.1.

VMware Fusion 5 and VMware Fusion 5 Professional are available immediately for download. Customers who purchased VMware Fusion 4 on or after July 25 are eligible for a free upgrade. VMware Workstation 9 is also available immediately. Customers who purchased VMware Workstation 8 between Aug. 1 and Sept. 30 are eligible for free upgrades.